Reciprocating piston-type machines of the type described are generally known. In this context, it may be a question of a compressor, thus, for example, of a compressor for the air conditioning system of a motor vehicle. Compressors of this kind are usually referred to as air-conditioner compressors, and include a housing, which encompasses an externally driven compressor unit or pump unit. The compressor unit designed, for example, as an axial piston machine, includes, in turn, at least one piston which is able to reciprocate in a cylinder block. It is customary for a compressor of this kind to be equipped with a plurality of pistons, which are reciprocated in the direction of their longitudinal axis in response to the rotation of a supporting plate over a swash plate or in response to the pivoting of a pivot plate or a pivot ring, in the case of a swash plate, the swash plate being mounted in a torsionally fixed manner in the housing. The housing is typically sealed by at least one housing cover which is screw-coupled to the housing, for example. In this context, the form of a ring nut that functions between the housing and the housing cover, or of a single thread or of a separate threaded ring can be used for the screw connection.
In the case of air-conditioner compressors having screwed-in, pressurized back covers, covers or cylinder heads, high axial forces are transmitted via the thread into the housing. In conjunction with the triangular threads (i.e. V-threads) typically used, these axial forces produce a radial pressure which is exerted via the thread on the housing. This radial pressure on the housing leads to relatively high peripheral stresses in the housing and increases the friction torque during the screw-in operation. Moreover, additional thermal stresses are superposed on these forces during operation and at standstill.